1. Field of the Invention
The present invention relates to a bed apparatus having a base plate, on which a mattress is placed, and which is arranged to be moved vertically to raise the upper half of the body of a user.
2. Description of the Related Art
A bed apparatus for a patient includes a so-called "reclining type bed apparatus" which is capable of facilitating a user whose strength has been declined to, for example, have a meal. The reclining-type bed apparatus has a structure formed such that a base plate disposed on a bed frame is divided into a plurality of plate sections in the lengthwise direction of the bed frame; and a portion of the plate sections corresponding to the upper half of the body of the user, that is, a back raising portion, is enabled to be reclined by a drive mechanism.
Therefore, when the back raising portion of the foregoing bed apparatus is moved upwards, a user facing upwards is able to raise the upper half of the body without using power.
When the back raising portion is moved upwards in a pivotal manner, the mattress placed on the base plate is bent while pressing the back side of the user. Since the mattress has a predetermined thickness, compressive force is generated in the upper portion of the inner portion of the mattress in a lengthwise direction toward the inside portion thereof when the mattress is bent by raising the back raising portion. On the other hand, tension is generated in the lengthwise direction in the lower portion of the mattress which is the outer surface of the bent mattress.
Therefore, also the compressive force generated in the upper portion of the mattress acts on the back of the user whose upper half of the body is raised while being pressed by the top surface of the mattress. Therefore, the back is pressed downwards by the compressive force and thus the hip and the femoral region are pressed rearwards (in a direction toward the back raising portion). As a result, the hip is held by the mattress and pressed excessively.
If the user is strong enough to raise the back from the top surface of the mattress to remove the compressive force acting on the back, no problem arises. However, if the user is too weak to remove the compressive force, the user feels a pain.